Synthesis and properties of polymer brush consisting of poly(phenylacetylene) main chain and poly(dimethylsiloxane) side chains

A novel polymer brush consisting of poly(phenylacetylene) (PPA) main chain and poly(dimethylsiloxane) (PDMS) side chains was synthesized by the polymerization of phenylacetylene-terminated PDMS macromonomer (M-PDMS). The macromonomer was prepared by the esterfication of monohydroxy-ended PDMS (PDMS-OH, degree of polymerization (DP) = 42) with p-ethynylbenzoic acid. The polymerization of M-PDMS using [(nbd)RhCl]₂/Et₃N catalyst led to polymer brush, poly(M-PDMS), with M_n up to 349?000 (DP of main chain 104). Poly(M-PDMS) with narrow molecular weight distribution (M_n = 39?900, M_w/M_n = 1.11) was obtained with a vinyl-Rh catalyst, [Rh{C(Ph)CPh₂}(nbd){P(4-FC₆H₄)₃}]/(4-FC₆H₄)₃P. Poly(M-PDMS)s were brown to orange viscous liquids and soluble in organic solvents such as toluene and CHCl₃. The UV-vis absorptions of poly(M-PDMS) were observed in the range of 350-525 nm, which are attributable to the PPA main chain.     

Crystalline morphology of poly(dimethylsiloxane)

The crystalline morphology of poly(dimethylsiloxane) was studied using a scanning electron microscope equipped with a cold stage. Samples of two different molecular weights were used. In both cases, spherulitic morphology is seen, from −70 °C, with spherulites of about 100 μ in size. Small single crystals of about a micron in size are also seen, and these are attributed to the presence of cyclics.     

Effect of filler amount on thermoelastic properties of poly(dimethylsiloxane) networks

End-linked poly(dimethylsiloxane) (PDMS) networks were prepared in the presence of fumed silica particles with hydroxyl groups at their surfaces. The silica particles were introduced into the polymer solution prior to end-linking. Hydroxyl ended PDMS chains were end-linked via the tetra functional crosslinker, tetraethoxysilane. The filler content varied in the range 0-5 wt%. Atomic Force Microscopy was used to image and characterize the silica particles. Swelling, stress-strain and thermoelasticity experiments were performed. The temperature coefficient and the energetic part of the force in uniaxial extension are found to increase with increasing silica amount. This observation is ascribed to effects contributed possibly by the adsorption layer around the silica particles.     

Structure-property behavior of poly(dimethylsiloxane) based segmented polyurea copolymers modified with poly(propylene oxide)

Poly(propylene oxide) (PPO) was incorporated in a controlled manner between poly(dimethylsiloxane) (PDMS) and urea segments in segmented polyurea copolymers and their solid state structure-property behavior was investigated. The copolymers contained PDMS segments of MW 3200 or 7000 g/mol and an overall hard segment content of 10-35 wt%. PPO segments of MW 450 or 2000 g/mol were utilized. Equivalent polyurea copolymers based on only PDMS as the soft segment (SS) component were used as controls. The materials (with or without PPO) utilized in this study were able to develop microphase morphology as determined from dynamic mechanical analysis (DMA) and small angle X-ray scattering (SAXS). DMA and SAXS results suggested that the ability of the PPO segments to hydrogen bond with the urea segments results in a limited inter-segmental mixing which leads to the formation of a gradient interphase, especially in the PPO-2000 co-SS containing copolymers. DMA also demonstrated that the polyureas based on only PDMS as the SS possessed remarkably broad and nearly temperature insensitive rubbery plateaus that extended up to ca. 175 °C, the upper temperature limit depending upon the PDMS MW. However, the incorporation of PPO resulted in more temperature sensitive rubbery plateaus. A distinct improvement in the Young's modulus, tensile strength, and elongation at break in the PPO-2000 and PDMS-7000 containing copolymers was observed due to inter-segmental hydrogen bonding and the formation of a gradient interphase. However, when PPO was incorporated as the co-SS, the extent of stress relaxation and mechanical hysteresis of the copolymers increased relative to the segmented polyureas based on the utilization of only PDMS as the soft segment component.     

Synthesis and physicochemical characterization of a well-defined poly(butadiene 1,3)-block-poly(dimethylsiloxane) copolymer

For the first time, order-order and order-disorder transitions were detected and characterized in a model diblock copolymer of poly(butadiene-1,3) and poly(dimethylsiloxane) (PB-b-PDMS). This model PB-b-PDMS copolymer was synthesized by the sequential anionic polymerization (high vacuum techniques) of butadiene 1,3 (B) and hexamethylciclotrisiloxane (D₃), and subsequently characterized by nuclear magnetic resonance (¹H and ¹³C NMR), size exclusion chromatography (SEC), Fourier Transform infrared spectroscopy (FTIR), Small-Angle X-ray scattering (SAXS) and rheology. SAXS combined with rheological experiments shows that the order-order and order-disorder transitions are thermoreversible. This fact indicates that the copolymer has sufficient mobility at the timescale and at the temperatures of interest to reach their equilibrium morphologies.     

Reactivity of poly(dimethylsiloxane) toward acidic permanganate

Poly(dimethylsiloxane) (PDMS) has been widely used in various microfluidic devices because it is considered to be one of the most inert materials available. A PDMS-based microfluidic system for the synthesis of manganese oxide (MO) nanoparticles is developed and tested. However, synthesis of MO nanoparticles in the PDMS-based microfluidic system is unsuccessful due to an unexpected reaction between acidic permanganate and PDMS. PDMS is pitted and coated with MnO₂ and opalized silica, which are confirmed by SEM and EDX. The products of the reaction between PDMS and acidic permanganate are mainly MnO₂, Cl₂, SiO₂ and CO₂, respectively. Here we report for the first time the reactivity of PDMS toward acidic permangante resulting in a new process to coat the channel walls with MnO₂.     

Synthesis, structure and morphology of poly(dimethylsiloxane) networks filled with in situ generated silica particles

The morphology of silica particles generated in situ in PDMS networks in the presence of two types of catalysts is evaluated by using different techniques including solid-state ²⁹Si MAS NMR, near-infrared spectroscopies and small-angle X-ray scattering. The interactions with the poly(dimethylsiloxane) chains are examined through the swelling properties and thermal characteristics (in particular crystallization process) of the composites. In addition, ¹H NMR is used to investigate the adsorption layer of reduced mobility on the particle surface.     

An investigation of the interaction of potassium ions with poly(dimethylsiloxane)

The interactions of potassium ions with , -hydroxy-terminated and , -trimethylsilyl-terminated poly(dimethylsiloxanes) (PDMS) have been investigated. After mixing with potassium hydroxide followed by partial extraction, the , -hydroxy-terminated PDMS samples gave elastomeric materials which are thought to result from aggregation of terminal potassium silanolate ion pairs. Uniaxial tensile testing of these materials was carried out at 298 K. The , -trimethylsilyl-terminated PDMS, when mixed with potassium hydroxide, however, gave completely soluble material following identical solvent extraction procedures.     

Manufacturing and characterizations of flexible poly(dimethylsiloxane)/poly(vinyl acetate)/polythiophene ternary composite films

ABSTRACT

In this study, polythiophene and poly(dimethylsiloxane)/poly(vinyl acetate)/polythiophene ternary composites were synthesized. The new ternary composites obtained in powder and film forms were characterized using various techniques. Magnetic properties of all the materials were analyzed by Gouy balance measurements, and it was found that their conductivity mechanism is of polaron nature. The surface structure, surface roughness, and thermal properties of the prepared samples were identified by Scanning Electron Microscopy, Atomic Force Microscopy, and Thermogravimetric Analysis, respectively. The tensile-tension test studies were performed for mechanical properties. The PDMS/PVAc/PT (6%) composite demonstrated about 50% of the maximum strain value (%) of vulcanized natural rubber.     

丙烯酸酯接枝硅油消泡剂的制备与性能

分别以丙烯酸甲酯接枝硅油(MA-g-PHMS)、丙烯酸乙酯接枝硅油(EA-g-PHMS)和丙烯酸丁酯接枝硅油(BA-g-PHMS)为原料,制得了3种有机硅乳液消泡剂;并用正交试验优化了工艺条件,优化后的条件分别为:MA-g-PHMS硅膏质量分数为24%,乳化剂质量分数为4%,于70℃反应5 h;EA-g-PHMS硅膏质量分数为24%,乳化剂质量分数为3%,于70℃反应4 h;BA-g-PHMS硅膏质量分数为24%,乳化剂质量分数为3%,于75℃反应6 h。3种消泡剂都具有高效的消泡性能,其中EA-g-PHMS消泡剂性能极佳,其消泡时间为10.1 s,抑泡时间为21.6 min。     

The miscibility and phase behavior of polyethylene with poly(dimethylsiloxane) in near-critical pentane

Miscibility and phase behavior of solutions of polyethylene (PE) and poly(dimethylsiloxane) (PDMS) mixtures in near-critical n-pentane have been investigated in a special variable-volume view-cell equipped with a computerized data acquisition system. This is a study on dissolving mutually incompatible polymers in a common solvent at high pressures. The fluid-fluid and fluid-solid demixing pressures of the solutions were determined for different polymer concentrations (5% PE, 5% PE+1% PDMS, 5% PE+2% PDMS and 5% PE+5% PDMS). In the PE+n-pentane solutions, the system shows LCST (lower critical solution temperature) type behavior and the fluid-fluid demixing pressures increase with increasing temperature. The PE+PDMS+n-pentane systems, however, show UCST (upper critical solution temperature) type behavior and the fluid-fluid demixing pressures decrease with increasing temperature. Even with small addition of PDMS to PE, the demixing pressures show dramatic increases compared to the demixing pressures of PE alone. At high PDMS concentrations (5% PDMS), complete miscibility could not be achieved at pressures up to 70 MPa. The fluid-solid boundary that is associated with the melting or crystallization of PE was also studied as a function of cooling and heating rates. It is shown that these temperatures tend to approach the same value in the limit of very low heating and cooling rates.     

Supramolecular assembled C60-containing carboxylated poly(dimethylsiloxane) composites

Supramolecular assembled nanocomposites were prepared through the solution casting of the complexing mixtures from the side chain carboxylated poly(dimethylsiloxane) (PDMS) with the 1-(4-methyl)-piperazinylfullerene (MPF). FT-IR and XPS analyses reveal that there are strong ionic interactions between the two components. Small-angle X-ray scattering study shows the formation of MPF fullerene nanodomains dispersed in the PDMS matrix, but no highly ordered structures, which is confirmed with TEM images. Compared to its polymeric precursor, the MPF crosslinked composites exhibit superior thermal mechanical stability and dramatic increase in the storage and loss moduli. Moreover, elastic response exceeds viscous response in the composites due to the formation of crosslinking structures. The increase of the MPF content in the composites leads to a denser packing of MPF nanodomains, resulting in better thermal, mechanical, and viscoelastic properties. The decrease in the carboxylic acid groups along the PDMS chains reduces the crosslinking density of the PDMS/MPF composites. The composites show a combined dielectric property from both PDMS and MPF components.     

Transport properties of organic vapours in silicone/clay nanocomposites

Poly(dimethylsiloxane) (PDMS)/clay nanocomposites have been synthesized using a novel ω-ammonium functionalized oligo-PDMS surfactant (PDMS-N⁺(CH₃)₃) and processed in membrane form. In order to relate the clay morphological structure to the degree of dispersion and physical properties of the membrane, the clay ion-exchanged by PDMS-N⁺(CH₃)₃ has been compared to a non-exchanged sodium MMT and to two organoclays organo-modified by using either non-functional alkyl ammonium cations (C₃₈H₈₀N⁺) or hydroxyalkyl ammonium (C₂₂H₄₈ON⁺) cations. Morphological analysis and transport properties (sorption, diffusion and permeability) have been investigated using two penetrants: acetone and n-hexane. The mechanical and rheological properties of the PDMS nanocomposite membranes have also been studied. It has been found a significant effect of the clay organo-modifier on the morphology, physical and barrier properties of the systems.     

ABA-type block copolymers containing poly(dimethylsiloxane) and ketonic resins

Block copolymer containing segments of poly(dimethylsiloxane) (PDMS) and ketonic resins were synthesized. Dihydroxy-terminated PDMS were reacted with the isophorone diisocyanate (IPDI) to obtain the diisocyanate-terminated PDMSs (urethane). These urethanes were reacted with reactive hydroxyl groups in the cyclohexanone–formaldehyde, acetophenone–formaldehyde, and in situ melamine-modified cyclohexanone–formaldehyde resins. Formation of block copolymers was illustrated by several characterization methods, such as chemical and spectroscopic analysis and gel permeation chromatography. The solubilities of the block copolymers were determined, and their surface properties were investigated by contact angle measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 643–648, 1998     

Surface segregation in blends containing poly(dimethylsiloxane)-polystyrene block copolymers

The surface composition of polystyrene blends containing poly(dimethylsiloxane)-polystyrene block copolymers have been analyzed using X-ray photoelectron spectroscopy (XPS), contact angle measurements, and time-of-flight secondary ion mass spectrometry (TOFSIMS). The three techniques showed the surface of the blend samples to be identical to pure poly(dimethylsiloxane) homopolymer, despite the fact that the systems each contained only a 2% bulk concentration of siloxane. The high surface sensitivity of TOFSIMS—which probes the samples to depths of a few angstroms—indicates an enrichment of-Si(CH₃)₃ groups at the surface. These are the terminal groups of the PDMS part of the block. Their enrichment at the surface of the samples is presumably due to their low surface energy, in addition to the tendency for end groups to be at the surface due to free volume considerations.Presented at the XXVIth Silicon Symposium, Indiana University-Purdue University at Indianapolis, March 26–27, 1993.     

Synthesis and properties of random poly(lactic acid)-based ionomers

A random poly(lactic acid), PLA, based ionomer was synthesized by copolymerizing a methacrylate-terminated PLA macromonomer and methyl methacrylate. The copolymerization kinetics were studied using ¹H NMR spectroscopy and the copolymer composition was characterized by ¹³C NMR spectroscopy. Carboxylic acid groups were introduced into the copolymer by reacting the hydroxyl end groups of the PLA macromonomer with succinic anhydride, and the acid groups were neutralized with metal acetates to produce Na-, Ca-, and Y-PLA ionomers. Significant increases in T_g were observed for the ionomers and thermomechanical analysis indicated that the ionomers were more resistant to penetration by a weighted probe and an apparent rubbery plateau was observed above T_g. The ionomers were more hydrophilic than PLA, but relatively low water absorption could be achieved for the Ca²⁺-salt ionomer.     

Synthesis of poly(phenylene oxide)-based fluoro-tin-oxide/ZrO2 nanoelectrode arrays by hybrid organic/inorganic approach

This paper describes the synthesis and the characterization of poly(phenylene oxide)-based nanoelectrode arrays. Using a hybrid organic/inorganic “sol–gel” solution, FTO (fluoro-tin-oxide) nanoelectrode arrays were synthesized with well-defined order, and controlled diameter of the nanoelectrode and the center-to-center distance. These FTO/ZrO₂ nanoelectrodes were modified with ultrathin, polymer coatings based on the self-limiting electropolymerization of phenol. The polymer coated mainly the FTO nanoelectrodes. Impedance coupled with FTIR spectroscopies studies shows that the electrodeposited polymer coating is uniform, conformal and pin-hole free. The CP-AFM (conductive probe-AFM) imaging studies confirm that the ultrathin, uniform insulating poly(phenylene oxide) (PPO) layer homogeneously coats the FTO nanoelectrodes.     

Interpenetrating polymer networks of poly(dimethylsiloxane): 1. Preparation and characterization

Model networks of ,ω-dihydroxy-poly(dimethylsiloxane) (PDMS) were prepared by tetrafunctional crosslinking agent tetraethyl orthosilicate (TEOS) and the catalyst stannous 2-ethylhexanoate. Hydroxylterminated chains of PDMS having molecular weights 15 × 10³ and 75 × 10³ g mol⁻¹ were used in the crosslinking reaction. Bimodal networks were obtained from a 50% (w/w) mixture of PDMS chains with M_n = 15 × 10³ and 75 × 10³ g mol⁻¹. A sequential interpenetrating network of these PDMS chains was also prepared. Physical properties of the elastomers were determined by stress-strain tests, swelling and extraction experiments, and differential scanning calorimetry measurements.     

Synthesis and some properties of polyoxyhexakis (dimethylsilylene) and its copolymers with dimethylsiloxane

The synthesis of polyoxyhexakis(dimethylsilylene).1. by the hydrolytic polycondensation of ,-dichlorohexakisdimethylsilylene,2. and by cationic ring-opening polymerization of dodecamethyloxahexasilacycloheptane.⁶D_j, initiated with a protic acid is reported. The possibility of synthesis of alternative copolymers composed of oxyhexakis(dimethylsilylene) units and dimethylsiloxane or oligodimethylsiloxane units were also explored. Polymers are characterized by NMR spectroscopy. Their thermal behavior is discussed.     

Block copolymer grafted-silica particles: a core/double shell hybrid inorganic/organic material

Hybrid inorganic/organic materials consisting of a poly(n-butyl acrylate)-b-poly(styrene) diblock copolymer anchored to silica particles were synthesized via ‘grafting from’ technique using a controlled/living free radical polymerization named stable free radical polymerization. XPS and FTIR analysis were used to control the effectiveness of the chemical modification of the silica particles. Thermal characterizations were performed by thermal gravimetric analysis (TGA) and by differential scattering calorimetry (DSC). The TGA permitted the determination of the quantity of grafted polymer and thus the grafting density; DSC was used to study the influence of the silica and blocks of the copolymer on their thermal behaviors. The glass transition temperature of the grafted copolymers was compared to these of free polymers or copolymers homologues.